Hello and welcome!
First of all, I'm sorry you are suffering. We all know what it's like to be in a r/s with pwBPD. The very first piece of advice I try to give newcomers is do NOT try to talk to them about their BPD, it will cause rages. pwBPD have incredible amounts of self-loathing and shame, and bring up 'imperfections' will cause him to lash out to protect himself.
The second piece of advice is to say take the time to read the lessons here, and do NOT let him know about the website. Same reason.
What I want to tell you is you are not alone, and we are all here to support each other

The biggest hurdle is learning how to communicate with our pwBPD in an effect manner and not taking their dysregulations personally. For a pwBPD, feelings=facts, and what they say they believe at the time... .but that can change within minutes.
What exactly does he think is your fault?